Fluid controlled transmission



May 5, 1953 Filed Aug. 25, 1950 V. F. STEWART FLUID CONTROLLEDTRANSMISSION 3 Sheets-Sheet l INVENTOR.

'VIRGIL E STEWART BY 4 V n m AT TORNEYS May 5, 1953 v. F. STEWART FLUIDCONTROLLED TRANSMISSION 3Sheets-Sheet 2 Filed Aug. 25, 1950 INVENTOR.

VIRGIL E STEWART BY ATTORNEYS 3 Sheets-Sheet 3 Filed Aug. 25, 1950 m m mm VIRGIL F. STEWART BY flldfi ATTORNEYS Patented May 5, 1953 UNITEDSTATES @ATENT OFFICE Claims.

1 This invention relates to. a variable speed transmission controlled bya fluid. coupling. It is particularly adapted for the transmission ofpower in the. engines of: automotive vehicles such as passenger cars,trucks, and bus-sea. However, the invention may be employed in variousenvironments. where rota-tire energy is to be transmitted from a primemover to: a driven device wherein variable. loads are encountered. A;transmission similar to the present type is disclosed in my co-pendingapplication, Serial No. 70,32l, filed January 11., 1949, now Patent No.2,543,378, issued March 6., 1951, the present application coveringimprovements made thereto.

The primary object of this invention is to provide a variabletransmission speed ratio and to achieve such ratio change automaticallyand without gear Shifting.

Another object of the invention is to provide a power transmissionmechanism which involves the principle oi diminishing ratio andincreasing ratio through the use of a fluid coupling and fixed gearingin constant mesh, the ratio diminishing. or increasing in directrelation to the applied load.

A further object of the invention is to provide a compact automatictransmission capable of easy manufacture and assembly which isparticularly well suited to the requirements of vehicles driven byinternal combustion engines.

(Ether objects and advantages of the invention, more or less ancillaryin nature will be apparent to those skilled in the art from theappended. description of the preferred embodiment of the invention andaccompanying drawings, in which:

l. is a longitudinal cross section of the transmission assembly;

Fig. 2 is an elevational view of the fluid coupling having parts thereofcut away;

Fig. 3 is a sectional view of the transmission gearing taken along line3s-3 of Fig. 1;

Fig. 4*. is a cross sectional view of the transmission gearing takenalong line i-t in Fig. l; and

Fig. 5 is an isometric schematic representation of the gear train andthe related fluid coupling.

The preferred, embodiment of the invention includes an oil-tightcircular case it which circumscribes and encloses the operable parts ofthe transmission. A power input shaft ii is joined to the case it by aplurality of cap screws l2 which maintain the centerline or" shaft ii incoincidence with the center of rotation of the case iii; thus therotative speed or" case it is equal to the speed of the input shaft andthe output l3 functions as the sun gear.

of the prime mover. A stub shaft 53 projects inwardly along the.centerline of case H3 and is joined thereto by the. cap screws it. Thestub shaft it has a pinion it formed thereon at the innermost endthereof.

The hydraulic coupling as illustrated in Fig. l and Fig. 2 includes adisc is projecting radially inwardly from the inner wall of case itwhich is afiixed thereto. A plurality of fins l5 joined to disc it by anumber of rivets ll or other suitable fabricating means are curvedradially inward so that the forward face of the blade is convex whenviewed from a point in advance of the blade as it rotates.

The driven rotor includes a disc it which is joined to a flanged hub it.A pair of antifriction bearings 2@ lie intermediate hub it and shaft i3and carries the hub is for relative rotation with the shaft iii. Aplurality of pockets 2i, preferably formed from a continuous strip ofthin metal, project laterally from disc l8 and are joined thereto by aplurality of rivets 22. The pockets 2i and fins it have clearance spacetherebetween to allow relative rotation. The

. coupling action, therefore, is accomplished by the fluid beingdischarged from the fin section against the pockets which are caused tomove as a result of the force applied thereto by the moving fluid. Itfollows that as casing it and fins it are rotated by the input shaft it,the oil will be pumped through the couplin and the driven rotor will berotated at a speed approaching that of the casing.

The transmission gearing is of the planetary type wherein pinion i l onthe end of drive shaft A pair of planet gears 23 engage sun gear Hi andare carried for rotation around said gear by two spider discs i l and25. A ring gear 23 circumscribes the gears 23 and. is in engagementtherewith. A radial flange 2? on ring gear 253 is afiixed to the hub ll}of the driven rotor. It is seen, therefore, that since ring gear itrotates with the driven rotor and sun gear i rotates with the casing andthe fins l5, relative motion in the coupling occurs only when theplanetary gears are rotating relative to sun gear it. Further, therelative. velocity between the driving and driven rotors is directlyproportional to the relative velocity of the planetary gears, and thespider around sun pinion i l.

Each of the planetary gears 23 has a pinion 2t integral and coaxialtherewith which drives the second planetary gear 28 carried for rotationby spider plates 2-; and The gears are relatively large as compared topinions 28 thereby producing a gear reduction relative to gears 23. Thering gear circumscribes and engages gears 29 and has a radial flange 3|integral with the output shaft and flange 32. The ring gear 30,therefore, rotates at the same speed as the input shaft 1 I when thereis no relative rotation in the planetary gears. However, due to theabove mentioned gear ratio between pinion 28 and gear 29, the speed ofring gear 30 will be reduced relative to ring gear 23 when planetarygears 23 and the spider rotate relative to sun gear M.

The spider plates 24 and 25 are held in spaced relationship by spacers33 which have one end thereof in threaded engagement with plate 25. Capscrews 34 hold plate 24 against the opposite end of spacers 33 and arethreadably mounted therein. Th spider plates are bored to receivetrunnions 35 on the planetary gears and thereby hold the gears forrotation on an axis parallel to the axis of rotation of case In and inthe proper spaced relationship to sun gear M and ring gears 26 and 30.Bearing plates 36 are mounted on the sides of the spider plates 24 and25 opposite to the planetary gears and absorb the thrust of theplanetary gears as they rotate in the spider. Plates 36 are held inabutting relationship to spider plates 24 and 25 by a series of screws31.

The spider is free to rotate in either direction relative to the caseand is carried for such rotation by needle-type bearings 38 locatedbetween spider plate 24 and shaft [3. A stub shaft 39 is joined tospider plate 25 and projects laterally therefrom along the centerlinethereof. Needle bearings 40 carry the shaft 39 for rotation within acounterbored portion of the output shaft 32. An antifriction bearing 4|is disposed to carry the end of case Ill opposite to input shaft II andis located between the inner margin of the radial flange on case I0 andshaft 32.

The oil circuit through the fluid coupling is completed through aplurality of ports 42 in disc 15 near the wall of easing l0 and througha number of openings 43 in the flange 21 of ring gear 26. Asubstantially circular path results from the coupling arrangement andthe aforementioned ports and prevents the loading up of the fluid in thecoupler elements.

Casing It is formed in two sections for assembly purposes, the sectionsbeing joined at their flanges by a row of bolts 44. A gasket 45intermediate of the casing flanges prevents leakage of fluid from theinterior of the coupling assembly.

In normal operation, the casing l0 and stub shaft l3 will be rotated asthe engine drives the transmission. For purposes of this specification,the normal operating condition will be considered as the low torque orno load condition during which no relative movement occurs between thedriving and driven rotors and the planetary gears are stationaryrelative to the sun gear. The speed of rotation of the output shaft willbe equal to that of the input shaft and the entire assembly will rotateas a unit.

If the rotation of output shaft 32 is resisted requiring a torque toovercome such resistance, this torque will be immediately transmittedthrough ring gear 30 to planetary gear 29, pinion 28 and planetary gear23. Sun gear l4 being aflixed to shaft II will be driven by the inputtorque and will oppose the rotation of gear 23 and thereby causerelative rotation therebetween. When this occurs, spider 24 will revolveand ring gear 26 will be made to rotate in a direction opposite to thatof the input shaft. Assuming no resistance to the rotation of ring gear23, it can be seen that the planetary system would be incapable oftransmitting torque from the input to the output shafts. It is obvioustherefore that a flexible locking effect must be introduced to overcomethe rotation of ring gear 26 and to cause the input torque to betransmitted through the assembly.

Reference to Fig. 5, a schematic diagram of the gear train assembly,will show how the fluid coupling is incorporated to provide thenecessary locking. Pump vanes l5 are amxed to the input shaft anddischarge to the driven rotor pockets 2! which are attached to ring gear26. Therefore, relative movement of ring gear 26 in an oppositedirection to the input shaft and driving rotor [5 will be overcome bythe coupling effect of the fluid between vanes l5 and pockets 2|. Theamount of coupling required will be that necessary to overcome thereaction caused by applying load to the output shaft.

Obviously, the force delivered to the driven baffle member by the oilprojected against it will be determined very largely by the realtivespeed of the two rotors. When the speed of the two members is the same,there will be no driving force, but as the load is imposed upon thedriven member, it will begin to rotate relative to the driving memberand the torque developed thereby will tend to carry the load. Theplanetary gear system used in this device will cause rotation of thespider member 24 at a speed which is proportional to the difference inthe speeds of the input shaft 32. The spider rotation causes the ringgear 26 to turn at a speed which is also proportional to the differencein speeds of the rotation of the input shaft and the output shaft. Itfollows therefore that the relative velocities of the fluid couplingelements and the torque provided thereby is determined by the relativerotation of the driving member and the driven member. As the speeds ofthese two members approach unity, the locking force or torque suppliedby the coupling diminishes.

It may be noted that the normal friction forces will add to the abovementioned locking effect of the coupling and serve to prevent relativerotation of the gearing in the planetary system when the output torquerequirement is low. Under this condition, there would be no loss ineither the gearing or the coupling. The normal cruising power requiredfor a vehicle is in this range and therefore, the ordinaryinefiiciencies are absent during the operation of this device undernormal conditions.

In starting the vehicle, the output shaft may be considered anessentially locked whereupon the power to the input shaft will causerotation at an ever increasing speed until suflicient force is obtainedfrom the transmission to cause rotation in the output shaft. During theinterval of increasing the torque, ring gear 3!! is stationary.Planetary gear 29 being driven by the pinion 28, gear 23, and sun gear I4 will rotate and travel around ring gear 30 thus producing a rotationin the spider. The ring gear 25 will be rotated as a result of thismotion in the spider, thus producing relative velocities between thedriving and driven rotors in the fluid coupling. As this coupling effectincreases with the speed change in the gearing, the locking torque willincrease therewith to a point where it is sufliassume cient to'resist afurther increase in the motion of. the spider whereupon ring gear 36will. cause rotation of the output shaft.

The effect of the planetary gear system is that of changing the gearratio 'so that the input torque may develop a muchhigher output torque.Asv the speed of the vehicle increases, and the output. torquedecreases, the gearing assembly with theaction of the fluid couplingwill gradually and automatically change gear ratio as required by theoutput load until it reaches unity at the low torque condition. The gearratio and the coupling may be selected to match the characteristics ofthe particular prime mover and load with which it is used. If the gearratio is too high, the engine may not reach a sufficient speed todevelop the necessary torque which will produce a suitable accelerationin the vehicle.

The braking effect of the engine is desirable in the operation of avehicle, particularly when travelling down grades. This effect ispresent in and is transmitted through this type of transmission by theaction of ring gear 30 and gear 29 in rotating the spider opposite tothe normal direction. Again, the ratio of the transmission changes andrelative velocities occur between the driving and driven rotors, thusproducing a torque and a locking effect on the transmission. The brakingeffect increases as the difference between the rotative speeds of theinput and the output shafts becomes greater, although the locking effectof the coupling will not be as strong when the action is reversed due tothe inefliciencies of the circulation caused by the blade shapes.

From the foregoing, it will be seen that the basic function of theplanetary gear system is to vary the speed difference between the inputand output members, and thereby increase the torque as required by theload to give the desired performance with the given prime mover. Suchmultiplication of torque is accomplished over a wide range withoutshifting of gears. Further, an infinite variation of gear ratios occurssmoothly and automatically as required by the load imposed on thetransmission.

Although the fOregoing description is necessarily of a detailedcharacter, in order that the invention may be completely set forth, itis to be understood that the specific terminology is not intended to berestrictive or confining, and that various rearrangements of parts andmodifications of detail may be resorted to without departing from thescope or spirit of the invention as herein claimed.

What is claimed is:

l. A power transmission device comprising a hydraulic coupling includingtwo elements relatively rotatable about a common axis having a mutualtorque reaction; a power input shaft and a power output shaft concentricwith the said axis, one of the elements being directly coupled to one ofthe said shafts; and gearing means coupled to both of the said shaftsand the other element, said means comprising a sun gear on said oneshaft, a spider mounted for rotation on said axis, a gear assemblycarried by said spider, a ring gear affixed to the other element, and asecond gear mounted on the output shaft, said assembly operably joiningthe sun gear and said ring gear and second gear.

2. A power transmission device comprising a hydraulic coupling includingtwo elements relatively rotatable about a common axis and having amutual torque reaction; a power input shaft and a. power output shaft.concentric with the said axis, one of the elements being directlycoupled to one of the said shafts; and gearing means coupled to both ofthe said shafts and the other elements; said means comprising a sun gearon said one shaft, a spider mounted for rotation on said axis, planetarygears carried by said spider in engagement with the sun gear, a ringgear affixed to the other element and in operable engagement with saidplanetary gears, and a second ring gear mounted on the output shaft andoperably joined with the planetary gears whereby the speed ratio betweenthe input and output shafts is a function of the difference in speedbetween the two elements.

3. A power transmission device comprising a hydraulic coupling includingtwo elements relatively rotatable about a common axis and having amutual torque reaction; a power input shaft and a power output shaftconcentric with the said axis, one of the elements being directlycoupled to one of the said shafts, the other element being operablycoupled to the other shaft, and means including a sun gear on said oneshaft, a spider mounted for rotation on said axis, a pair of gearscarried by said spider joined for rotation as a unit on a common axis,one of said pair of gears being in engagement with said sun gear, anidler gear mounted for rotation on the spider, said idler gear engagingthe other of said pair of gears, and a ring gear mounted on the outputshaft for engagement with said idler gear.

a. A power transmission device comprising a hydraulic coupling includingtwo elements relatively rotatable about a common axis and having atorque reaction; a power input shaft and a power output shaft concentricwith the said axis, one of the elements being directly coupled to one ofsaid shafts, the other element being operably coupled to the othershaft, and means including a sun gear on said one shaft, a spidermounted for rotation on said axis, a pair of gears carried by saidspider joined for rotation as a unit on a common axis, one of said gearsbeing in engagement with said sun gear, an idler gear mounted forrotation on the spider, said idler gear engaging the other of said pairof gears. and a ring gear mounted on the output shaft for engagementwith said idler gear, said one gear of the pair of gears beingrelatively larger than the other of said pair of gears.

5. A power transmission device comprising a hydraulic coupling includingtwo elements relatively rotatable about a common axis and having amutual torque reaction; a power input shaft and a power output shaftconcentric with the said axis, one of the elements being directlycoupled to one of the said shafts, the other element being joined to aring gear, and means including a sun gear on said one shaft, a spidermounted for rotation on said axis, a pair of gears carried by saidspider joined for rotation as a unit on a common axis, one of said pairof gears being in engagement with said sun gear and said ring gear, anidler gear mounted for rotation on the spider, said idler gear engagingthe other of said gears, and a second ring gear mounted on the outputshaft for engagement with said idler gear, said one gear of the pair ofgears being relatively larger than the other of said pair of gears, saididler gear being relatively larger than the other of said gears wherebysaid first ring gear rotates at a higher speed 7 than said second ringgear as the spider rotates Number relative to the input shaft. 2,448,249VIRGIL F. STEWART. 2,523,619 2,543,878 References Cited in the file ofthis patent 5 UNITED STATES PATENTS Number Number Name Date 442,5521,949,816 Smith-Clarke Mar. 6, 1934 450,953 2,311,150 Buraczynski Feb.16, 1943 2,314,253 Stewart Mar. 16, 1943 Name Date Bonham Aug. 31, 1948Grebb Sept. 26, 1950 Stewart Mar. 6, 1951 FOREIGN PATENTS Country DateGreat Britain Feb. 11, 1936 Great Britain Apr. 24, 1935

